Supplemental inflatable restraint systems (SIRSs) require air bag closure assemblies to prevent vehicle occupants from tampering with the system and to provide a path through which air bags may deploy into vehicle passenger compartments. Some prior art SIRS closure assemblies include at least one air bag door that is hinged to swing open in response to air bag inflation. This type of door may be mid-mounted on the front vertical face of an instrument panel as shown in U.S. Pat. No. 3,708,179 or may be mounted on an upper surface of an instrument panel or dash board as shown in U.S. Pat. No. 5,498,027.
An air bag closure assembly of this type must have some means of holding the air bag door closed over the air bag deployment opening in the vehicle instrument panel. Such means must be able to secure the air bag door against occupant tampering but must readily release the door when an air bag deploys. For example, U.S. Pat. No. 5,498,027 issued Mar. 12, 1996 to Kelley et al. discloses an air bag closure assembly mounted over an air bag deployment opening in an automotive instrument panel. The air bag closure assembly includes a generally rectangular door supported and spaced above the instrument panel on a generally rectangular doorframe. Fasteners secure the doorframe to an upper surface of the instrument panel around the deployment opening. The door is hinged along one edge to open upward and away from the doorframe, providing a path for an air bag through the instrument panel. Foam layers are formed over the respective upper surfaces of the door and the doorframe. A skin is bonded to an upper surface of the door foam layer and marginally overlaps the door along three of four peripheral edges. The marginally overlapping portions of the door skin are draped over the three non-hinged door edges and are bonded to respective side surfaces of the door frame foam layer. This forms a seam between the foam layer and a surrounding applique or trim piece that clearly outlines the location of the air bag door. When a deploying air bag forces the door to open upward, the opening door tears loose the marginally overlapping portion of the door skin from the side surfaces of the door frame foam layer.
For aesthetic purposes, it is desirable for air bag closure systems of this type to include some means for concealing the air bag door from the view of vehicle occupants. It is especially desirable that such means provide a smooth unbroken, unmarked instrument panel upper or outer surface that includes no seams, edges or other discontinuities that might betray the presence of a supplemental inflatable restraint system. It is also desirable that such systems include some means for preventing the air bag door from breaking free of the instrument panel and flying loose in the passenger compartment.
One well-known method of concealing an air bag door is to mount the door such that the door outer surface lies flush with the instrument panel outer surface. A skin is then bonded across the outer surfaces of the air bag door and the instrument panel to hide the seam between the door and the panel. Air bag closure/deployment systems of this type will also include either some implement to cut through or initiate tearing in the skin when the air bag deploys, or a hidden tear seam formed on the lower side of the skin. However, the addition of a cutting implement and the formation of a hidden tear seam each require at least one additional step in the process of manufacturing an air bag door cover assembly.
What is needed is an air bag door cover assembly that includes means for concealing the air bag door and securing the door against occupant tampering and from breaking free during air bag deployment. What is also needed is such an assembly that has an improved appearance, reduced weight, fewer parts and is less expensive to manufacture.